Ground or soil aeration has changed over the years. Originally, soil aeration was accomplished by a farm type tractor pulling or towing a rather large roller. The roller would have ridges or spikes inserted in a random pattern or they would be inserted in horizontal lines. The aerator itself presented little problem for the tractor to pull or tow. If the aerator became wedged or stuck in the soil, the tractor would simply pull the aerator free.
Self-propelled aerators were developed to meet the need for a less expensive way to aerate soil without the use of large farm type equipment. Typically, a motor of some type was mounted onto a wheeled platform along with a spiked drum or a series of spiked wheels. The motor would drive the drum or wheels and propel the wheeled platform forward.
Self-propelled aerators that derive their forward or reverse momentum from the aerator portion of the apparatus tend to be uncontrollable. Steering, for example, becomes impossible because the rotating aerator has a tendency to dig-in when certain types of soil are encountered. For small irregular sized plots of ground steering of the aerator becomes paramount.
Attempts in the past to correct this problem involved aligning the spikes on the aerator horizontally with the ground surface. This attempt yielded a ground aerator that would jerk or jump from one row of spikes to another as the aerator rotated thus exasperating the user trying to steer the aerator. If the horizontal rows of spikes were placed closer together, the desired ground aeration would suffer. If the spikes were randomly placed about the drum, the desired ground aeration would suffer because to aerated holes would overlap or there would be an absence of aerated holes in the ground.
One such attempt incorporated a fertilizer machine with a ground aerator, U.S. Pat. No. 1,887,334 issued to Spaeth on May 14, 1931. The Spaeth patent discloses a ground aerator that has an aerating drum with spikes horizontally aligned on its surface. The fertilizer hopper is positioned above the spiked drum and is powered by the rotating drum. When the drum rotates the spikes, an engaged mechanical arm allows the contents of the hopper to be spread over the area traversed by the spiked drum. The Spaeth's ground aerator relies on the horizontal alignment of the spiked drum to propel the aerator and operate the metering mechanism located in the hopper.
Another attempt is U.S. Pat. No. 2,545,059 issued to Ward on Jun. 3, 1948 discloses a ground aerator and a material spreading machine that is self-propelled. The Ward patent discloses a spiked drum, a hopper, and a metering device for dispensing the material from the hopper. The Ward patent like the Spaeth patent relies on the horizontal alignment of the spikes attached to the drum.
An example of the random placement of spikes on the surface of an aerator is U.S. Pat. No. 2,778,291 issued to Kerns on Oct. 19, 1954. Kerns's patent discloses a ground aerator and a material spreading machine that is pulled or towed by a tractor. The material spreading device is positioned to the rear of a spiked surface that engages the ground to aerate. The spikes of the Kerns's patent are placed in channels and the channels are randomly spaced about the surface of the aerator.
It would desirable to have a self-propelled ground aerator that is easy to steer or maneuver on small or irregular sized plots of ground. The desirable aerator would also have the ability to aerate soil in the forward and reverse direction.